A Landscape-Level Analysis of Piping Plover Winter Habitat
Climo, Lisa. 1998. A Landscape-Level Analysis of Piping Plover Winter Habitat. M.S. thesis. University of Minnesota, Minneapolis.
While Piping Plover (Charadrius melodus) breeding biology has been well studied, much less is known about their wintering ecology and distribution, even though Piping Plovers spend 7-8 months annually on their wintering grounds. Conservation of the species will require greater knowledge of nonbreeding habitat use and availability. Objectives of this analysis were to describe landscape-level characteristics of suitable Piping Plover nonbreeding habitat using remote sensing and GIS technologies and to develop a spatial model to predict potential Piping Plover habitat on the bird's wintering grounds.
Locations of 50 shorebird winter survey sites were buffered to distances of 500 m, 1 km and 2.5 km, and overlaid onto land cover maps of the Gulf Coast counties of Florida produced with Landsat Thematic Mapper satellite imagery. Amounts of seven cover types within each distance were compared between sites with and without Piping Plovers. Amounts of open water were significantly higher (p < 0.001) and amounts of marsh and urban areas were lower (p < 0.01 and p < 0.05, respectively) at present sites than at absent sites at all three scales. The higher proportion of water around plover-occupied sites is indicative of the peninsular-type landscapes associated with Piping Plover occurrence in Florida. These high-energy environments may provide the type of barren beach where cryptic plovers can safely roost, and/or the type of tidal flat upon which Piping Plovers can most effectively forage, or the most suitable juxtaposition between these two microhabitats.
I developed two predictive models based on the significantly different land cover types around plover prsent and absent sites (alpha = 0.05; for one model I used the 500 m-scale statistics, and for the other I used the 1 km-scale statistics. Correct classification rates for the training data set were 70% for the 500 m model, and 72% for the 1 km model. Both models had a 50% correct classification rate for the 8 sites in Florida used to test the models. The models were unsuccessful in accurately predicting Piping Plover habitat in the Coastal Bend-Laguna Madre Region of Texas. Results of this analysis indicate that although Piping Plovers are associated with certain landscape configurations, parameters used to develop a model at this scale in one region may not be useful to predict suitable habitat over the bird's entire winter range.
Conservation implications of this study: This study is the first known attempt to evaluate and describe Piping Plover winter habitat on a landscape scale. Although the reasons why Piping Plovers select certain habitats are still unclear, Piping Plovers seem to be associated with landforms that provide tidal flats for foraging and open beaches for roosting within unobstructed movement of each other. These microhabitats may be present at a single site, or may be provided by several nearby sites within a habitat complex. The implication of this hypothesis is that human activity that obstructs such movement between roosting and foraging areas will adversely affect Piping Plovers. For example, urban development on a barrier island that currently has no vertical obstructions to movement between ocean beach and lagoon tidal flat microhabitats could greatly reduce the amount of usable habitat for plovers by impeding movement between roosting and foraging areas. Structures that alter water movement such as seawalls or jetties could change Piping Plover habitat by altering the extent and/or arrangement of foraging and roosting sites within a local area. And, while the most highly used Piping Plover sites warrant habitat protection efforts, these sites should also be viewed in a broader context to determine if nearby secondary sites are important to the birds during certain times of the tidal cycle. The landscape-scale aspect of what constitutes Piping Plover habitat is thus an important consideration for winter habitat conservation. Further research directed towards determining landscape-scale patterns of habitat use in other parts of the bird's winter range, and examination of Piping Plover movement between roosting and foraging microhabitats, will help clarify the generality of apparent patterns and habitat relationships detected in this study.